The Search feature allows you to search for ideas on your Board with different filters:
By keywords
By colors
By categories
By number of likes
When you click on Search, 
(bottom right) your Board grays out to highlight the idea you are looking for.
You can return to your Board (not grayed out) by clicking again the Search button again.
To find out more about how to set up your Board, see the articles available on this link.